Process for the production of fertilizers



Patented Sept. 18, 1928.

UNITED STATES,

PATENT OFFICE.

MAX PAUL NITSCHE, OF DRESDEN, GERMANY.

PROCESS FOR THE PRODUCTION OF FERTILIZERS.

No Drawing. Application filed September 25, 1926,

always prevented the adoption or use as fer-' t-ilizer was the considerable amount of fixed and free sulphurousacid in the waste liquors. An attempt was made to combine the sulphurous acid with lime or other bases and thus make it innocuous. In practice however it was found that the less strong carbonic acid also liberates the sulphurous acid from the sulphites and thus injuries or destroys the plant growth. It was alsofoundthat the fixed 0 sulphurous acid in the waste liquors cannot be liberated from the compounds it forms with bases, but in the course of time splits off of itself from these compounds andthen acts just as detriment-ally upon the living vege table organisms.

It is known in analytical chemistry that the whole of the sulphur-ous acid can be expelled from the waste liquors by phosphoric acid. Other strong non-volatile. aclds have the same effect, with the exception of sulphurlc acid.

In the evaporation of the waste liquors, this latter acid exerts a strong oxidizing action and burns the organic substances, while being itself reduced to sulphurous acid.

It has been found that a salt whlch has not hitherto been employed,-the ac1d salt of sulphuric acid, viz, a bisulphate,is very suitable for completely expelling the sulphur- 40 ous acid from the waste liquors, wlthout the organic substances contained in the same being destroyed.

In order to increase the fertilizing Value of the fertilizer obtained in this manner use is preferably made of potassium blsulphate. The sulphurous acid 1n the waste liquors is determined beforehand and then when evaporating the amount of potassium bisulphate equivalent thereto is added.

means of a vacuum apparatus.

The' advantage of this process is twofold.

Preferably evaporation is carried out by Serial No. 137,816, and in Germany October 8, 1925.

In the first place the whole of the sulphur-ous acid 1s recovered and can be returned to the process again and moreover a very good fertilizer for the soil is obtained. The, bacteria of the soil which combine with nitrogen, Vigorously absorb as a nutrient, the carbohydrates etc. contained therein and owing to their vitality combine with large quantities of nitrogen from the air. The soil treated with this fertilizer does not therefore require to be fertilized with nitrogen, more especially as the enriching of the soil'with nitrogen is perceptible for some length of time. If necessary this fertilizer can be mixed beforehand with bacteria cultures which are capable of combining with nitrogen, in order to inoculate soils poor in bacteria simultaneously when applying the fertilizer.

The other salts contained in this fertilizer, for instance the potassium and calcium salts etc. as well as the phosphoric acid of plant origin, increase very considerably the fertilizing value of the fertilizer produced by this process.

The residues obtained in this manner in the evaporation by means of a vacuum apparatus have neutral to acid properties. Surplus acid is preferably rendered innocuous by means of lime or Thomas meal.

Example.

To a sulphite cellulose waste liquor, containing 5,84 kg. fixed and 2,56 kg. free sul' phurous acid, that is to say in all 8,40 kg. sulphurous acid, expressed in cbm., 35,71 kg. p0- tassium bisulphate are added per cbm. and evaporated in a vacuum.

Since practically 100 kg. solid residues are left from one cbm. waste liquor, 127,2 kg. of fertilizer are formed with the potassium bisulphate and 8,4 kg. sulphurous acid. The latter is returned to the process. The sulphurous acid removed in the evaporation can be collected and used for the preparation of fresh quantities of sulphite cellulose.

What I claim is 1. A method of producing a fertilizer from sulphite Waste lye which is obtained in the manufacture of sulphite cellulose, consisting in adding an acid salt of sulphuric acid to the lye and subjecting the resulting liquor to evaporation, whereby the sulphurous acid is and subjectin the resulting liquor to evaporemoved and a. residue is obtained which conration, where y the bisulphate is removed stitutes the fertilizer. and a. residue is obtained which constitutes l0 2. A method of producing a fertilizer from the fertilizer. 5 sulphite waste lye which is obtained in the In testimony whereof I have signed my manufacture of sulphite' cellulose, consistname to this specification. ing in adding potassium bisulphate to the lye MAX PAUL NITSCHE. 

